Is there a repeater in the controller for the hall riser? There should be for a duplex. Make sure the termination resistance is correct, should have 60 ohms on each side of the repeater with power off. For the riser that’s a 120 ohm resistor at the last HNB and the termination jumper on the repeater on. For the controller side, both CPUs should have all the termination jumpers on and the repeater jumper off. Make sure the 24vdc after the repeater is solid.